1. It is all about PRASM and not loads or demand. This really means loads at the right place. I am certain that for the right price, UA can fill 4 daily services.
2. Looking at this as West Coast - Australia O&D is a narrow view of the market. There is East Coast and to a certain extent Europe to Australia as well as onwards traffic in Asia.
Finally, all of this has to take place in the context of what other aircraft, crew and related staff UA has at its disposal or which may be obtained in the timeframe.
Not as easy a proposition as it first seems.